Whale arrival date forecast validation, 2007 and 2008

Weather forecasters enjoy (or lament) the gratification of finding out how good their forecasts are just a few days after making them. Ecosystem forecasters, on the other hand, often have to wait a long time before we know. One of our forecasts is for the arrival date of right whales in the Great South Channel critical habitat. Each year we try to predict when the whales will arrive in large numbers to feed there. Then we wait, sometimes for years, for the data to come in, so that we can see which predictions are correct, and which need to be re-examined, and why.

We now have the right whale sightings data from 2007 and 2008, so the moment of truth is at hand. I haven't dug into the analysis yet, but here is the first cut. Our 2007 prediction was very close, falling just a few days from the actual arrival date, and falling well within the predicted window (see figure). Our 2008 prediction was later than the arrival date. This appears to be driven by a period in mid March when there were lots of whales, followed by a lull. Use of the habitat picked up again in mid April, and persisted from there. Our model appeared to pick up on this later arrival, missing the brief but intense party in mid March. It'll be interesting to dig into this further when we start our analysis, and see if we can shed light on what was happening in mid March.

Figure Right whale sightings per unit effor in the Great South Channel for 1998-2008. Black line indicates the arrival date computed from the data (day at which sightings per unit effort crosses 0.01). Horizontal boxes indicate the arrival date forecast for each year. Figure is preliminary.